Risk management
Position Sizing in Forex: A Practical Guide
How fixed-fractional position sizing in forex works: set a risk amount, measure the stop, convert pip value, round lots down and cap correlated exposure.
Position size is the one variable you control completely on every trade. Entry timing, the stop and the target all depend on the market. The number of lots is a decision you make before the order goes in, and it decides how much a loss costs. A good entry with the wrong size can still do serious damage to an account.
This guide covers fixed-fractional sizing, a common starting point for systematic traders, and the mechanics that trip people up: pip value in a different account currency, lot-step rounding and positions that are really the same bet.
The fixed-fractional rule
Fixed-fractional sizing risks the same percentage of current equity on every trade. If you risk 1% and your account is $10,000, a full stop-out costs $100. If the account grows to $12,000, the next stop-out costs $120. If it shrinks to $9,000, it costs $90.
The formula has three inputs:
Lots = Risk amount ÷ (Stop distance in pips × Pip value per lot)
The order of operations matters. You set the stop where the trade idea is proven wrong, then size the position so that the stop costs your chosen amount. Moving the stop to fit a preferred lot size reverses the logic and usually puts the stop somewhere the market can reach for no reason.
The three inputs
| Input | What it is | Where it comes from |
|---|---|---|
| Risk amount | Equity × risk percentage | Your account balance or equity and your risk rule |
| Stop distance | Pips between entry and stop | The chart and the trade plan |
| Pip value per lot | Money gained or lost per pip on 1.00 lot | The pair, the lot size and your account currency |
Use equity rather than balance if you already hold open positions, because floating losses are real exposure. The pip value input is where most mistakes happen. If you need a refresher on pip size and the three quote cases, read the guide to pips.
Worked example: USD account on EUR/USD
- Account equity: $10,000
- Risk per trade: 1%, so the risk amount is $100
- Pair: EUR/USD, stop 25 pips from entry
- Pip value: $10 per standard lot (100,000 units), because the quote currency is the account currency
Loss per lot at the stop is 25 × $10 = $250. Lots = $100 ÷ $250 = 0.40 lots.
Check it backwards: 0.40 lots × 25 pips × $10 = $100. If the backward check does not land on your risk amount, one of the inputs is wrong.
Cross-currency accounts
When the account currency appears nowhere in the pair, pip value has to be converted. Take a euro account trading USD/JPY:
- Account equity: €20,000
- Risk per trade: 0.5%, so the risk amount is €100
- Pair: USD/JPY at 150.00, stop 35 pips
- Pip value in the quote currency: 0.01 × 100,000 = ¥1,000 per lot
- Conversion: EUR/JPY at 162.00, so ¥1,000 = €6.17 per pip per lot
Loss per lot at the stop is 35 × €6.1728 = €216.05. Lots = €100 ÷ €216.05 = 0.4629.
The conversion rate moves while the trade is open, so pip value in your account currency drifts too. For a trade held a few days the effect is usually small next to slippage, but for positions held for weeks it is worth recalculating. The pip value calculator does this conversion for the main account currencies.
Rounding to lot steps
Brokers accept volume in fixed steps, often 0.01 lots, with a minimum trade size. Check the symbol's volume step on your platform rather than assuming.
Always round down. In the euro example, 0.4629 lots rounds down to 0.46 lots, which risks 0.46 × €216.05 = €99.38. Rounding up to 0.47 would risk €101.54, which breaks the rule by a small amount every time and adds up over hundreds of trades.
Small accounts hit the minimum lot size quickly. Consider a $500 account risking 1% ($5) on EUR/USD, where 0.01 lots is worth $0.10 per pip:
| Stop distance | Loss at 0.01 lots | Calculated size | What you can trade |
|---|---|---|---|
| 30 pips | $3.00 | 0.0167 lots | 0.01 lots, risking $3.00 |
| 60 pips | $6.00 | 0.0083 lots | Nothing within the $5 limit |
When the calculated size is below the minimum lot, the honest answer is to skip the trade or accept a higher risk percentage knowingly. Quietly trading the minimum lot means the risk rule exists only on paper.
Correlated exposure
Fixed-fractional sizing treats each trade on its own. Markets do not. Long EUR/USD and long GBP/USD are both short the US dollar. If you risk 1% on each and the dollar rallies hard, both stops can be hit in the same move, and you have effectively risked 2% on a single view.
The same thing happens with less obvious pairs. Long EUR/USD and short USD/CHF are both bets against the dollar. Long AUD/USD and long NZD/USD often trade like one position.
Two practical controls:
- A per-currency cap. Add up the risk on every open position that shares a currency exposure in the same direction and keep the total under a ceiling you set in advance, for example 1.5% for any one currency.
- A total open-risk cap. Limit the sum of risk across all open trades, for example 4% to 5% of equity, so a broad shock cannot take out more than that in one session.
These numbers are illustrations rather than recommendations. The right ceiling depends on how many positions you run and how correlated your instruments have been in your own trade history.
How fixed-fractional sizing behaves in a drawdown
Because the risk amount shrinks as equity falls, a losing streak hurts slightly less than a flat-dollar approach. Ten consecutive 1% losses leave 0.99^10 = 90.44% of the starting equity, a drawdown of 9.56% rather than 10%. The trade-off is that recovery is also slower, since the next winners are sized from a smaller base.
What fixed-fractional sizing does not do is make an account safe. Risk per trade combined with win rate and payoff ratio decides how deep drawdowns can get and how likely you are to hit a level you cannot tolerate. The guide to risk of ruin covers that calculation, and the position size calculator applies the formula above with the conversions done for you. Trading leveraged products carries a real risk of loss whichever method you use.
Key points
- Set the stop from the trade idea first, then size the position so the stop costs a fixed fraction of equity.
- Lots = risk amount ÷ (stop pips × pip value per lot), and the backward check should return your risk amount.
- Convert pip value into your account currency whenever the account currency is not the quote currency.
- Round lot sizes down to the broker's volume step, and skip trades that cannot be sized within the rule.
- Count correlated positions as one exposure and cap total open risk.